The present invention relates to an inspecting method and an inspecting apparatus for inspecting the surface roughness existing on the surface of a substrate such as a semiconductor substrate or a hard disk substrate.
In a manufacturing line for the semiconductor substrate or thin film substrate, the inspection for defect or foreign matter existing on the surface of the semiconductor substrate or thin film substrate is made to maintain and improve the yields of products. For example, in a sample such as a semiconductor substrate before forming a circuit pattern, it is required to detect a microscopic defect or foreign matter (hereinafter called a defect) of 0.05 μm or less on the surface or microroughness (haze) on the surface. Also, to detect such defect, the conventional inspecting apparatus applies a condensed laser beam to the surface of the sample and condenses and detects a scattered light from the defect. Also, in a sample such as a semiconductor substrate after forming the circuit pattern, the sample surface is illuminated by a laser beam, a scattered light occurring on the sample surface is condensed, a diffracted light from a periodical pattern is shielded by a spatial filter, a scattered light from a non-periodic pattern and the defect is detected, and the non-periodic pattern is deleted by die comparison to recognize the defect.
A semiconductor inspection among various kinds of substrate inspection will be described below by way of example. On a wafer after to passing through various kinds of semiconductor manufacturing process for a silicon wafer or film formation, there are various defects, which decrease the yields of the semiconductor products. As a degree of integration of the semiconductor product is increased, it is required that the surface inspection of the substrate has the higher sensitivity and the defects are classified and is detected. There are various kinds of defects such as foreign matter, scratch and COP (crystalline defect), and further there is recently a demand for detecting the microroughness on the surface of the substrate.
These prior arts were described in patent document 1 (JP-A-2003-130808), non-patent document 1 (APPLIED OPTICS 1995 Vol. 34, No. 1 pp. 201-208), non-patent document 2 (P. A. Bobbert and J. Vlieger (Leiden Univ.): Light Scattering), non-patent document 3 (S. O. Rice, Comm. Pure and Appl. Math 4, 351 (1951)), non-patent document 4 (J. M. Elson; Light scattering from surfaces with a single dielectric overlayer; J. Opt. Soc. Am. 66, 682-694 (1976)), non-patent document 5 (J. M. Elson: Infrared light scattering from surface covered with multiple dielectric overlayers; Appl. Opt. 16, 2872-2881 (1977)), and non-patent document 6 (J. M. Elson: Multilayer-coated optics: guided-wave coupling and scattering by means of interface random roughness; J. Opt. Soc. Am. A12, 729-742 (1995)).